Date: Mon, 16 Feb 1998 15:58:17 -0800 From: Mike Smith <mike@smith.net.au> To: Tor Egge <Tor.Egge@idi.ntnu.no> Cc: mike@smith.net.au, toor@dyson.iquest.net, hackers@FreeBSD.ORG Subject: Re: VM messed: vm_page_free panic problem Message-ID: <199802162358.PAA08389@dingo.cdrom.com> In-Reply-To: Your message of "Tue, 17 Feb 1998 00:42:48 %2B0100." <199802162342.AAA16968@pat.idi.ntnu.no>
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> > In the case in question, this is to be expected. The MFS is supposed > > to be in the kernel image, but because the 4MB page covering the kernel > > is not correctly set up an early MFS operation causes a fatal fault. > > > > Your fix is probably correct in the general case, but it's not relevant > > here. > > It is relevant. > > I probably gave too little information in my previous mail. I think so. Thanks for taking the time to elaborate. > The kernel backtrace shown was for a slightly modified (DDB was added) > 3.0-SNAP install kernel. The program to be started was "/stand/sysinstall". > > Without a mfs_getpages, I got the crash. > > With a mfs_getpages, the kernel booted fine, and I got the normal > sysinstall menu. Ah. It wasn't clear to me that you had actually done this. > DISABLE_PSE was not specified in the kernel config file for any > of these (modified) 3.0-SNAP install kernels. It should not be needed > to use this option at all. I concur, as does Bruce. I couldn't see what was wrong with either the before or after cases, merely that DISABLE_PSE made things work. > The main difference between running 3.0-CURRENT from hard disk and and > installing a 3.0-SNAP from a floppy is how the MFS file system is used. > Reading/writing files does not cause a VOP_GETPAGES() call, but a > VOP_STRATEGY() call, which is supported by MFS. Would this mean that in "normal" use, attempting to execute something off an MFS would also cause problems? [... explanation ...] > It is not obvious to me how using the DISABLE_PSE option fixes this > problem. Nor to me. At that point I was happy that it resolved the immediate issue. > The problem probably started occuring with revision 1.76 of kern_exec.c, > dated `1998/02/05 03:32:04', which changed the pagein behavior when > starting new processes. That would be consistent with the observed symptoms. Thanks for the fix; it looks as though I was, indeed, chasing yet another wrong (but oddly functional) answer to the problem. I owe you a beer. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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